Acoustic signals are typically generated by moving membranes causing pressure variations which results in propagation of acoustic waves. Speakers and speaker systems are often integrated into various electronic devices and may be constructed in different configurations to produce acoustic waves of audio-band frequency ranges.
Some types of speaker elements (acoustic transducers) utilize Piezo-electric materials to generate mechanical movement in response to electric field applied on the material. Many piezo-electric materials can provide mechanical movement at frequencies corresponding to acoustic frequencies (as well as other frequency ranges) and can be used to generate acoustic signals in the audio band and/or ultrasound ranges.
U.S. Pat. No. 6,427,017 discloses a piezoelectric diaphragm with a transparent piezoelectric member and a transparent electrode. Also disclosed is a portable electronic device that has a display means to display an image and a piezoelectric speaker having a transparent piezoelectric member and a transparent electrode. In this portable electronic device, the piezoelectric speaker is disposed in front of the display means.
US 2011/033,074 provides a transparent speaker which is suitable for being disposed on a display panel. The transparent speaker includes a transparent membrane, a transparent electrode plate, and spacers. Each transparent electrode plate has a plurality of openings. The display panel includes a plurality of pixels. The pixels emit optical signals. A Moire spatial period of the optical signals is less than 600 μm after the optical signals pass through the transparent speaker. When the transparent speaker is disposed on the display panel, a user is able to watch an image on the display panel through the transparent speaker without being interfered by a Moire.
US 2011/261,021 describes a haptic device including a substantially transparent composite piezoelectric cell configured to measure a deformation of a surface of the cell and to provide a haptic feedback effect as a result of the deformation. More specifically, US 2011/261,021 discloses a haptic device comprising: a substrate; and a substantially transparent composite piezoelectric cell overlaying the substrate, the piezoelectric cell comprising a sensor piezoelectric layer configured to generate a first signal when the sensor piezoelectric layer is deformed, and an actuator piezoelectric layer configured to provide a haptic effect upon receipt of a second signal that is based on the first signal.